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1、Figure 9-12 Tool-nose radius compensation allows us toprogram the part, not the tool path. The mathematical calculations that are needed to program a part profile with angles and radii, without the aid of cutter diameter compensation, can be very involved.on a turning center. When we set the X and Z
2、 axes of the tool, we create a square point on the tool. Most of the tools we use for turning have radii. To compensate for the radii, we need to use TNR compensation, which saves us from having to mathematically calculate the cutter path (see Figure 9-12).TNR compensation also lets us use the same
3、program for a variety of tool types. With TNR compensation capabilities, the insert radius size can be ignored and the part profile can be programmed. The exact size of the cutting tool to be used is entered into the offset file, and when the offset is called, the tool path will automatically be off
4、set by the tool radius.Tool-nose radius compensation can be to the right or left of the part profile.To determine which offset you need, imagine yourself walking behind the cutting tool. Do you want the tool to the left of the programmed path or to the right (see Figure 9-13)? Figure 9-13 Tool-nose
5、compensation.Compensation direction is controlled by a G-code. When a compensation to the left is desired, a G41 is used. When a compensation to the right is needed,a G42 is used. When using these cutter compensation codes, you need to specify how much the controller is to offset. The size of the ra
6、dius is placed in the nose radius offset table, which is typically located adjacent to the tool file under the tool number being used. Tool-nose radius information can be determined from catalogs or the insert package.Other information needed to insure proper compensation is the tool nose direction
7、vector. The tool tip or imaginary tool tip of turning tools has a specificlocation or direction from the center of the tool-nose radius. The tool nose vector tells the control which direction it must compensate for individual types of tools.Standard tool-nose direction vectors are shown in Figure 14
8、. The direction vector number is usually placed in the same tool offset table as the radius value. Figure 9-14 Tool-nose radius direction vectors.To invoke compensation, the programmer will have to make a machine move (ramp on). This move allows the control to evaluate its present position and make
9、the necessary adjustment from tool-edge positioning to tool-nose radius positioning. This adjustment move must be greater than the radius value of the tool. To cancel the cutter compensation and return to cutter-edge programming, the programmer must make a linear move (ramp off) to invoke a cutter c
10、ompensation cancellation (G40).Figure 9-15 illustrates a typical part that uses tool-nose radius compensation.The program for the part follows the figure. N0001 G90 G20; N0005 G40; N0010 T0101; N0015 G92 X5.800 Z10.250; N0020 G96 S400 M03; N0025 GOO G42 Xl .30 Z.100; (Rapid position ramp on move and
11、 TNR compensation to the right) N0035 GOO X.375; (Profile of the part) N0045 G01 Z0.0 F.01; (Profile of the part) N0050 G01 X.500 Z-.0625; (Profile of the part) N0055 G01 Z-1.00; (Profile of the part) N0060 G02 Xl .00 Z-1.25 1.25 K0.0; (Profile of the part) N0065 G01 X1.25; (Profile of the part)N007
12、0 G40 G00 X2.0 Z2.0; (TNR compensation cancel and rapid positionramp off move)N0075 G28;N0080 T0100;N0085 M30; Figure 9-15 Program that utilizes tool-nose radius compensation.CANNED CYCLES FOR TURNING CENTERSCanned cycles (fixed) cycles are used to simplify the programming of repetitive turning oper
13、ations, such as rough turning, threading, and grooving. Canned cycles are sets of preprogrammed instructions that eliminate the need for many lines of programming. Programming a simple part without the use of a canned cycle can take up to four or five times the number of lines needed for a part prog
14、rammed with canned cycles. Think of the lines that are needed to produce a thread: (1) position the X and Z axes to the proper coordinates with a rapid traverse move (G00), (2) position the tool for the proper lead angle, (3) feed the tool across, (4) rapid position the tool back to the clearance pl
15、an, (5) feed the tool across. That is only two threading passes. With a canned threading cycle, a thread can be done with one line of programming. Standard canned cycles, or fixed cycles, are common to most CNC machines. See Figure 9-4 for a general list of the most commonly used canned cycles for t
16、urning centers. ROUGHING OR TURNING CYCLE (G71)The G71 automatically takes roughing passes to turn down a workpiece to a specific diameter at a specified depth of cut. The G71 cycle reads a specified number of blocks to determine the part profile and determines each pass, the depth of cut for each pass, and the number of repeat passes for the cycle. Cutti
